1. Field of the Invention
The present invention relates to a composition for protecting a resist that provides good results when applied to fine processing in the manufacturing of a semiconductor device, a mask, a magnetic head, etc., as well as a multi-layer body, a method for forming a resist pattern, a method for manufacturing a device having a pattern by fine processing and an electronic device that use the composition.
2. Description of the Related Art
In response to the elevation of the level of integration of LSI, the pattern resolution has entered a very fine region of 0.1 μm or less. Accordingly, it is indispensable to establish a fine processing technology that can cope with the resolution level. In the field of lithography, forming a finer pattern using an exposure light source with a shorter wavelength, or even using electron beams, X-rays, or the like, is being studied to respond to the requirement. In particular, the electron-beam lithography and X-ray lithography are considered to be second-generation light exposure technologies, and it is an urgent issue to develop a resist technology and pattern formation technology that have a high sensitivity and a high resolution to correspond to these technologies.
As a resist that can correspond to the electron-beam lithography and X-ray lithography, a chemically amplified resist comprising a photo-acid generating agent {see, for example, U.S. Pat. No. 4,491,628 (claims), Proc. Microcircuit Eng. (J. M. J. Frechet et al., p. 260, 1982), Digest of Technical Papers of 1982, Symposium on VLSI Technology (H. Ito et al., p. 86, 1983), and Polymers in Electronics, (H. Ito et al., ACS Symposium Series 242, ACS, p. 11, 1984)} is considered to be promising. With this chemically amplified resist, as easily understood from the above-described references, an acid is generated from a photo-acid generating agent by the irradiation of UV rays, electron beams, X-rays, focused ion beams, etc., and exposed parts are turned into an alkali-soluble (positive type) material or alkali-insoluble (negative-type) material by means of baking after the light exposure, utilizing the catalytic reaction. Owing to this, an apparent quantum yield can be improved, and a higher sensitivity is realized. A chemically amplified resist comprises a base resin, a photo-acid generating agent, various additives, and a solvent, in general. A cross-linking agent is further added, in the case of a negative-type resist.
It is to be noted that, in the light exposure with electron beams, a charge-up phenomenon, that is accumulation of electric charges, occurs during the light exposure owing to the fact that the resist is an insulative material, which causes a problem of deviation of locations of the resist pattern (poor patterning). For the purpose of avoiding this problem, a film from an electroconductive resin or antistatic resin, that is a resist-protecting film, is formed on the resist to prevent accumulation of electrons {see Japanese Unexamined Patent Application Publication No. 4-32848 (claims) and No. 8-109351 (claims)}.
Resins for forming this resist-protecting film generally indicate basicity due to reasons for the manufacturing or the like, and accordingly, there is a problem that when such a resist-protecting film is formed on a chemically amplified resist layer, it neutralizes the acid generated from the resist in the vicinity of the interface, resulting in poor resolution in the case of a positive-type resist, and thinning of the film in the case of a negative-type resist. This will be explained using FIGS. 1, 2, 3 and 4 schematically illustrating side cross-sectional views of multi-layer bodies having a chemically amplified resist layer and resist-protecting film on a substrate. FIGS. 1 and 2 are examples of a positive type resist, and FIGS. 3 and 4 are examples of a negative-type resist.
FIG. 1 illustrates a multilayer body 11 as it is irradiated with electron beams, where hydrogen ions (H+) of an acid are generated in a positive-type resist layer 2 on a substrate 1. In this case, bases (indicated as X−) in a resist-protecting film 3 acts to neutralize the hydrogen ions. Therefore, the amount of the hydrogen ions is particularly insufficient in the vicinity of the interface 4 with the resist-protecting film, and thus, the part does not indicate sufficient solubility at the development, with the result that in the multilayer body 12 after the development, the edges 6 of the insoluble parts 5 result in a T-type poor resolution (T-top) as illustrated in a letter T in FIG. 2. Numeral 7 indicates a space that is formed by dissolution/removal of the resist.
In contrast, FIG. 3 illustrates a multilayer body 31 as it is irradiated with electron beams, where hydrogen ions (H+) of an acid are generated in a negative-type resist layer 2. In this case, bases (indicated as X−) in a resist-protecting film 3 acts to neutralize the hydrogen ions. Therefore, the amount of the hydrogen ions is particularly insufficient in the vicinity of the interface 8 with the resist-protecting film, and thus, the part does not indicate sufficient insolubility at the development, with the result that in the multilayer body 32 after the development, thinned film parts 9 (round top) occur due to rounding of the edges and thinning of the resist layer as shown in FIG. 4.
In order to solve this problem, a measure is taken to add an acidic compound to the resist-protecting film. However, an acidic compound works the other way and accelerates the reaction of the resist in the vicinity of the interface between the resist-protecting film and resist layer, causing poor resolution in the case of a negative-type resist and film thinning in the case of a positive-type resist. This will be explained using FIGS. 5, 6, 7 and 8 schematically illustrating side cross-sectional views of multi-layer bodies having a chemically amplified resist layer and resist-protecting film on a substrate. FIGS. 5 and 6 are examples of a positive type resist, and FIGS. 7 and 8 are examples of a negative-type resist.
FIG. 5 illustrates a multilayer body 51 as it is irradiated with electron beams, where hydrogen ions (H+) of an acid are generated in a positive-type resist layer 2. In this case, hydrogen ions (indicated as H+) of the acidic compound in a resist-protecting film 3 act to add to the action of the hydrogen ions in the resist layer at sections that have been irradiated with the electron beams, and also cause the reaction in the resist layer even at those sections that have not been irradiated with the electron beams, with the result that such sections show excessive solubility at the development, and accordingly, the multilayer body 52 after the development has a thinned resist layer with thinned parts 9 having round edges, as shown in FIG. 6.
In contrast, FIG. 7 illustrates a multilayer body 71 as it is irradiated with electron beams, where hydrogen ions (H+) of an acid are generated in a negative-type resist layer 2. In this case, acidic ions (indicated as H+) of the acidic compound in a resist-protecting film 3 cause the reaction in the resist layer even at those sections that have not been irradiated with the electron beams, with the result that such sections become insoluble at the development, and accordingly, the edges 6 of the insoluble parts 5 result in a T-type poor resolution in the multilayer body 72 after the development, as shown in FIG. 8.
With such problems at the background, a method for forming a pattern using a resist-protecting film (also simply referred as “protecting film” in this specification) that can prevent accumulation of electric charges without affecting normal formation of a resist pattern, is being desired.
It is an object of the present invention to solve such poor patterning problems and to provide a technology by which fine patterns are consistently obtained. Other objects and advantages of the present invention will be clarified through the following explanation.